Background: Selecting the most suitable embryos for implantation and subsequent healthy live birth is crucial to the success rate of assisted reproduction and offspring health. A promising alternative is the non-invasive imaging of live embryos to establish metabolic activity performance. However, metabolic imaging has been only achieved using highly complex advanced microscopy methods that are costly and challenging, limiting the potential for deployment within fertility clinics. Thus, we aimed to develop an affordable and scalable optofluidic device capable of non-invasively obtaining high-resolution 3D images of the metabolic activity in live mouse embryos.
Method: Optofluidic devices were manufactured by cast-moulding using a negative photoresist (MicroChemicals GmbH-Germany) following a standard UV-photolithography process. The microstructures fabricated of PDSM integrated Light Sheet Fluorescence Microscopy into a microfluidic system, including on-chip micro-lenses to generate a light sheet at the center of a microchannel. Super-ovulated F1 (CBA/C57Bl6) mice were used to produce 2-cell embryos and embryo culture experiments. Blastocyst formation rates and embryo quality (immunocytochemistry) were compared between study groups. Furthermore, inhibition of metabolic activity (FK866 inhibitor) during embryo culture was also assessed. A convolutional neural network (CNN; ResNet 34) model using metabolic images was also trained.
Results: The results indicated no significant difference between the imaged and non-imaged embryos for embryo development as well as embryo quality at the blastocyst stage (p>0.05). Embryos with inhibited metabolic activity by FK866 showed a decrease in blastocyst formation as well as a reduction in metabolic activity measured by non-invasive metabolic imaging compared to controls (Control: 0.75 arbitrary units [AU]; Inhibitor: 0.5 AU; p<0.0001). Metabolic images predicted blastocysts formation with an AUC of 0.92.
Conclusion: This study reports an optofluidic device capable of non-invasive metabolic imaging of live embryos using a similar concept as previously reported using FLIM technology and hyperspectral microscopy.